The present invention relates to solid state light emitting devices and, in particular, to those with a specified optical path and wavelength output.
Prior solid-state lighting devices typically use a light emitting diode (LED), an organic light emitting diode (OLED), or a laser diode (LD) as part of a remote phosphor system combined with one or more remote phosphors which convert a portion of the initial emitted radiation into a usable spectrum. A remote phosphor system is a combination of a reflective or transparent substrate, such as plastic, acrylic, glass, etc., that has a phosphorescent powder deposited on its surface. This substrate can then convert the initial emitted light, usually blue or blue-violet coherent light, into broad spectrum non-coherent light, which is most commonly white light.
These devices already outperform incandescent and fluorescent light sources with advantages that include longer lifetimes, energy savings, and brighter light output. However, while systems similar to those described above have been employed for some time, they still have issues that inhibit the technology. These issues include a low efficiency conversion of the laser light, the non-conversion of some or most of the laser light, the emission of dangerous coherent light, and the difficulty of controlling the direction and optical path of the emitted converted light.
For these reasons, the overall efficiency of the extant designs remains comparatively low, even when LD-based devices (the most efficient design) are analyzed. Furthermore, prior designs that use an LD to provide the primary light input completely saturate the remote phosphor elements. This over saturation can lead to the inadvertent emission of coherent laser light, which can cause damage to sensitive electronics, materials, eyes, and skin.
Thus, there is a need in the art for an improved solid state light source that has an extremely high operation and conversion efficiency, and is safe to use in multiple environments.